University of Nebraska - LincolnDigitalCommons@University of Nebraska - LincolnPublications, Agencies and Staff of the U.S.Department of Commerce U.S. Department of Commerce

2016

Towards an ecosystem-based approach of Guam'scoral reefs: The human dimensionMariska WeijermanNOAA Fisheries, Pacific Islands Fisheries Science Center, 1845 Wasp Blvd Building 176, Mail Rm 2247, Honolulu, HI,mariska.weijerman@noaa.gov

Cynthia Grace-McCaskeyUniversity of Hawai'i at Manoa, Joint Institute for Marine and Atmospheric Research, 1000 Pope Road, Marine Science Bldg312, Honolulu, HI

Shanna L. GrafeldUniversity of Hawai'i at Manoa, Department of Natural Resources and Environmental Management, 1910 East-West Road,Sherman 101, Honolulu, HI

Dawn M. KotowiczUniversity of Hawai'i at Manoa, Joint Institute for Marine and Atmospheric Research, 1000 Pope Road, Marine Science Bldg312, Honolulu, HI

Kirsten L.L. OlesonUniversity of Hawai'i at Manoa, Department of Natural Resources and Environmental Management, 1910 East-West Road,Sherman 101, Honolulu, HI

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Weijerman, Mariska; Grace-McCaskey, Cynthia; Grafeld, Shanna L.; Kotowicz, Dawn M.; Oleson, Kirsten L.L.; and van Putten, IngridE., "Towards an ecosystem-based approach of Guam's coral reefs: The human dimension" (2016). Publications, Agencies and Staff of theU.S. Department of Commerce. Paper 546.http://digitalcommons.unl.edu/usdeptcommercepub/546

AuthorsMariska Weijerman, Cynthia Grace-McCaskey, Shanna L. Grafeld, Dawn M. Kotowicz, Kirsten L.L. Oleson,and Ingrid E. van Putten

This article is available at DigitalCommons@University of Nebraska - Lincoln: http://digitalcommons.unl.edu/usdeptcommercepub/546

Marine Policy 63 (2016) 8-17

Towards an ecosystem-based approach of Guam's coral reefs: The human dimension Mariska Weijerman a,b,*, Cynthia Grace-McCaskeyc, Shanna L. Grafeld d,

Dawn M. Kotowicz c, Kirsten L.L Oleson d, Ingrid E. van Putten e,f

a NOM Fisheries, Pacific Islands Fisheries Sdence Center, 1845 Wasp Blvd Building 176, Mail Rm 2247, Honolulu, HI 96818, USA b Wageningen University, Environmental Systems Analysis Group, PO Box 47, 6700M Wageningen, The Netherlands C University of Hawai~ at Manoa, Joint Institute for Marine and Atmospheric Research, 1000 Pope Road, Marine Sdence Bldg 312, Honolulu, HI 96822, USA d University of Hawai~ at Manoa, Department of Natuml Resources and Environmental Management, 1910 East-West Road, Sherman 101, Honolulu, HI 96822, USA e CSIRO Oceans and Atmosphere, GPO Box 1538, Hobart, TAS 7001, Austmlia f University of Tasmania, Centre for Marine Sodoecology, Hobart, TAS 7001, Austmlia

ARTICLE INFO

Article history: Received 10 July 2015 Received in revised form 24 September 2015 Accepted 24 September 2015

Keywords: Marine resource use Coral reef ecosystem Socio-ecological model Guam Fisheries Tourism

1. Introduction

ABSTRACT

Management of tropical reef ecosystems under pressure from terrestrial and extractive marine activities is not straightforward, especially when the interests of extractive and non-extractive marine resource sectors compete. Before implementing management actions, potential outcomes of alternative man­agement strategies can be evaluated in order to avoid adverse or unintended consequences. In tropical reef ecosystems the continued existence of the cultural and recreational fishing activities and the eco­nomically important dive-based tourism and recreation industry rest on sustainably managed marine resources. Through a case study of Guam, an ecosystem model was linked with human behavior models for participation in fishing and diving to evaluate future socio-ecological impacts of different manage­ment options. Ecosystem indices for reef status and resilience, and extraction potential were identified to evaluate the performance of alternative management scenarios. These marine ecosystem indices link the natural system to human uses (fishing and dive-based tourism and recreation). Evaluating management scenarios indicate that applying a single management tool, such as input controls or marine preserves, without also managing the watershed, is suboptimal. Combining different management tools has ne­gative near-term costs, particularly for the fishing sector, but these are likely to be outweighed by the long-term benefits obtained from greater species abundance. Adopting watershed management mea­sures in addition to fishery regulations distributes the burden for improving the reef status across multiple sectors that contribute to reef pressures.

© 2015 Published by Elsevier Ltd.

Ecosystem-based management is increasingly advocated for marine fisheries around the world [1,2]. Typically, different man­agement strategies could be implemented to achieve the man­agement objectives specified in an ecosystem approach. Manage­ment strategy evaluation (MSE), which compares and contrasts outcomes across multiple management objectives, is a tool im­plicit to an ecosystem approach [3,4]. One MSE approach involves the development of integrated marine ecosystem models, which requires intimate knowledge of the biophysical as well as the

socio-economic systems [5,6]. Integrated models can simulate the ecological, social, and economic consequences of different man­agement approaches [7-9]. Changing human behavior is the main management lever, and thus a critical component of integrated ecosystem modeling [10]. However, human behavior models of non-commercial activities are seldom coupled to biophysical­economic models.

Typically, these integrated models depict economic behavioral drivers quantitatively through the use of metrics, such as profit maximization [11]. Yet these models fail to capture the significant, non-commercial element of the fishery system, where fish might be taken for cultural or traditional celebrations, household con­sumption or barter [5,12,13]. Moreover, this commercial focus on extraction ignores the significant economic importance of non­market and non-extractive uses of the marine ecosystem [14].

* Corresponding author at: NOM Fisheries, Pacific Islands Fisheries Science Center, 1845 Wasp Blvd Building 176, Mail Rm 2247, Honolulu, HI 96818, USA.

E-mail address: Mariska.weijerman@noaa.gov (M. Weijerman).

http://dx.doi.org/10.1016/j.marpo1.2015.09.028 0308-597X/© 2015 Published by Elsevier Ltd.

Both reef-fish fisheries and reef-related tourism and recreation

Towards an ecosystem-based approach of Guam's coral reefs: Thehuman dimension

Mariska Weijerman a,b,n, Cynthia Grace-McCaskey c, Shanna L. Grafeld d,Dawn M. Kotowicz c, Kirsten L.L. Oleson d, Ingrid E. van Putten e,f

a NOAA Fisheries, Pacific Islands Fisheries Science Center, 1845 Wasp Blvd Building 176, Mail Rm 2247, Honolulu, HI 96818, USAb Wageningen University, Environmental Systems Analysis Group, PO Box 47, 6700AA Wageningen, The Netherlandsc University of Hawai'i at Manoa, Joint Institute for Marine and Atmospheric Research, 1000 Pope Road, Marine Science Bldg 312, Honolulu, HI 96822, USAd University of Hawai'i at Manoa, Department of Natural Resources and Environmental Management, 1910 East-West Road, Sherman 101, Honolulu, HI96822, USAe CSIRO Oceans and Atmosphere, GPO Box 1538, Hobart, TAS 7001, Australiaf University of Tasmania, Centre for Marine Socioecology, Hobart, TAS 7001, Australia

a r t i c l e i n f o

Article history:Received 10 July 2015Received in revised form24 September 2015Accepted 24 September 2015

Keywords:Marine resource useCoral reef ecosystemSocio-ecological modelGuamFisheriesTourism

a b s t r a c t

Management of tropical reef ecosystems under pressure from terrestrial and extractive marine activitiesis not straightforward, especially when the interests of extractive and non-extractive marine resourcesectors compete. Before implementing management actions, potential outcomes of alternative man-agement strategies can be evaluated in order to avoid adverse or unintended consequences. In tropicalreef ecosystems the continued existence of the cultural and recreational fishing activities and the eco-nomically important dive-based tourism and recreation industry rest on sustainably managed marineresources. Through a case study of Guam, an ecosystem model was linked with human behavior modelsfor participation in fishing and diving to evaluate future socio-ecological impacts of different manage-ment options. Ecosystem indices for reef status and resilience, and extraction potential were identified toevaluate the performance of alternative management scenarios. These marine ecosystem indices link thenatural system to human uses (fishing and dive-based tourism and recreation). Evaluating managementscenarios indicate that applying a single management tool, such as input controls or marine preserves,without also managing the watershed, is suboptimal. Combining different management tools has ne-gative near-term costs, particularly for the fishing sector, but these are likely to be outweighed by thelong-term benefits obtained from greater species abundance. Adopting watershed management mea-sures in addition to fishery regulations distributes the burden for improving the reef status acrossmultiple sectors that contribute to reef pressures.

& 2015 Published by Elsevier Ltd.

1. Introduction

Ecosystem-based management is increasingly advocated formarine fisheries around the world [1,2]. Typically, different man-agement strategies could be implemented to achieve the man-agement objectives specified in an ecosystem approach. Manage-ment strategy evaluation (MSE), which compares and contrastsoutcomes across multiple management objectives, is a tool im-plicit to an ecosystem approach [3,4]. One MSE approach involvesthe development of integrated marine ecosystem models, whichrequires intimate knowledge of the biophysical as well as the

socio-economic systems [5,6]. Integrated models can simulate theecological, social, and economic consequences of different man-agement approaches [7–9]. Changing human behavior is the mainmanagement lever, and thus a critical component of integratedecosystem modeling [10]. However, human behavior models ofnon-commercial activities are seldom coupled to biophysical-economic models.

Typically, these integrated models depict economic behavioraldrivers quantitatively through the use of metrics, such as profitmaximization [11]. Yet these models fail to capture the significant,non-commercial element of the fishery system, where fish mightbe taken for cultural or traditional celebrations, household con-sumption or barter [5,12,13]. Moreover, this commercial focus onextraction ignores the significant economic importance of non-market and non-extractive uses of the marine ecosystem [14].

Both reef-fish fisheries and reef-related tourism and recreation

Contents lists available at ScienceDirect

journal homepage: www.elsevier.com/locate/marpol

Marine Policy

http://dx.doi.org/10.1016/j.marpol.2015.09.0280308-597X/& 2015 Published by Elsevier Ltd.

n Corresponding author at: NOAA Fisheries, Pacific Islands Fisheries ScienceCenter, 1845 Wasp Blvd Building 176, Mail Rm 2247, Honolulu, HI 96818, USA.

E-mail address: Mariska.weijerman@noaa.gov (M. Weijerman).

Marine Policy 63 (2016) 8–17

are dependent on the condition of the reefs, which are presentlyunder heavy pressure in many parts of the world [15,16]. Effectivemanagement of coral reef resources must consider continued ex-istence of these valuable extractive and non-extractive resourceuses as well as the health of the marine ecosystem upon whichthey depend [17]. In this study, a dynamic reef biophysical modelis linked with human behavior models for the coral reef ecosystemof Guam. In Guam, tourism is one of the major contributing eco-nomic activities to Guam's gross domestic product [18] and reef-fish fishing is mainly conducted for social or cultural reasons [5].Despite the importance of a healthy reef ecosystem, the status ofGuam's marine resources has deteriorated over the past few dec-ades [19,20]. Guam's reefs have been stressed by poorly executedcoastal development and high sediment load from fallow landburning in southern upstream watersheds [20,21]. Inadequatesewage treatment systems and septic tanks have increased thenutrients and bacterial load in coastal waters [22,23]. Crown-of-thorns seastar predation outbreaks, which can be connected withhigh nutrient concentrations in the waters [24], have caused corallosses [20]. Fishing activities have caused a decline or loss ofecologically important fish species [25–27]. This combination offactors has led decision-makers to actively seek alternative man-agement approaches and tools to guide them [28].

The socio-ecological model developed in this study has three

main components: a quantitative ecological component and qua-litative fishery and tourism human behavior components. Com-bined, these three components can be used to simulate anthro-pogenic impact scenarios and their ecological effects and viceversa. The management scenarios considered were developed inconsultation with local resource managers from three agencies inGuam, and include removing existing marine preserves (MPs) andimplement catch and/or size limits and reducing land-basedsources of pollution through improved watershed management.While coral reef quality increases under some management sce-narios, indicators that are important to the dive industry, such asthe biomass of charismatic species, remain low. A managementscenario that trades off some reduction in reef-fish landingsagainst an increase in the ecological attributes that are favored bydivers could be preferable.

2. Case study: Guam

Guam, which became an unincorporated territory of the UnitedStates in 1950, is the largest and southernmost island in theMariana Archipelago of the western Pacific Ocean (between 13.2°Nand 13.7°N and between 144.6°E and 145.0°E; Fig. 1). Guam in avolcanic island with an area of approximately 549 km2 and a

Fig. 1. Location of Guam in the western Pacific Ocean (inset map) and the spatial model (Atlantis boxes) of the Guam Atlantis Coral Reef Ecosystem model showing humanpopulation density, creel survey zones and the depth contours.

M. Weijerman et al. / Marine Policy 63 (2016) 8–17 9

shoreline of about 187 km (129 km adjacent to coral reefs) [20].The human population of Guam is estimated at 159,358 in-dividuals [29]. Chamorros, the earliest inhabitants of Guam,comprise the largest ethnic group at 37.3% of the population [29],Filipinos make up 26.3%, followed by other Pacific Islanders(12.0%), whites (7.1%), and other Asians (6.0%). Nearly 10% of thepopulation identify themselves as having two or more ethnicities[29].

Guam's Gross Domestic Product was $4.88 billion in 2013 [30],primarily based on tourism and the U.S. military. In 2013, Guamhad approximately 1.3 million visitors of whom 70% were fromJapan [31]. The tourism sector is estimated to contribute between18% and 35% of local employment [5]. The U.S. military is thesecond largest contributor to Guam's economy; its economic im-portance has increased in the last few years, and is expected tocontinue to grow with the relocation of thousands of US Marinesand their dependents [32].

2.1. Marine resource use in Guam

For Guam, fishing and diving are two important reef-basedactivities directly reliant on the status and ongoing sustainable useof Guam's coral reef ecosystems.

2.2. Diving in Guam

Guam residents as well as tourists participate in between256,000 and 340,000 dives on Guam's reefs every year [18].Thirteen legal dive outfitters operate on Guam and offer betweenone dive and up to four dives per day during peak seasons [31].Additionally, there are anecdotal reports of some unregistered diveoperators.

An estimated 6% of 1.34 million annual visitors go scuba divingwhile on Guam, and 3% of tourists visit Guam with scuba diving asthe primary motivation for their trip [33, dive shop owner pers.comm. November 2014]. Although most tourists who visit Guamare from Japan, visitors from other Asian countries such as SouthKorea, Philippines, Taiwan, Hong Kong, Russia, and China havesignificantly increased in recent years [33]. This shift in the de-mographics of tourism is particularly relevant as the participationin dive trips varies by country of origin, with tourists from HongKong and Taiwan being far more likely to participate in scubadiving than tourists from Japan, the US, and Korea (Table 1).

2.3. Fishing on Guam

While diving is a popular non-extractive use of Guam's coralreef resources, reef fishing is an important extractive use of marineresources [18]. Guam's near-shore reef fishery is a multispeciesand multi-gear fishery. Fishing occurs from boats and from shoreinvolving trolling (mostly for pelagic fish), net fishing (e.g., castnet, gillnet, and surround net), and spearfishing (snorkel andscuba). Over the years gear methods have evolved and, new, moreefficient catch methods used, some with detrimental impact. Forinstance, the relatively new practice of spearfishing on scuba has

been linked to a decrease in large-size fishes leading to a targetingof smaller fish prior to reaching sexual maturity [25,34].

It is estimated that between 35% and 45% of Guam's householdswere involved in near-shore fishing [18]. Much of the fish caughton Guam is not traded in the market (and is not recorded incommercial statistics) but is instead eaten within the household orshared with family and friends. A 2005 survey of Guam house-holds found that out of the fish consumed by households, nearlyone-quarter (24%) was caught by the respondent or anothermember of the household, and an additional 14% was caught by afriend or extended family member [18]. The social obligation toshare one's fish catch extends to all fishermen [35]. This culturalpractice is particularly important among Guam's Chamorro re-sidents, who often give a large proportion of their catch to family,friends, and the local community [36,37]. Some of the other socialreasons to go fishing include spending time with family andfriends, to provide fish for a particular event or to teach membersof the younger generation traditional fishing practices. Thesepractices have non-market value as they can underpin socialnetworks and cultural ties throughout the Pacific Islands region[36].

3. Methods

In this study a quantitative biophysical model of the coral reefecosystems around Guam [38,39] was linked with qualitative be-havior models of two reef-dependent sectors (coral reef fishingand dive tourism). The ecosystem model was based on the Atlantisframework and was developed in consultation with communityexperts (Appendix A) at workshops on Guam in November 2012and June 2014. The aim of the Guam Atlantis model was to build avirtual coral reef ecosystem for managers and biologists to explorequestions and provide a tool to undertake scenario analyses. Themodel integrates best available data from multiple disciplines,such as hydrology and marine biology, at multiple scales. Detailscan be found in Weijerman et al. [38] and Weijerman et al. [39].

Atlantis is a deterministic model spatially resolved in threedimensions that tracks nutrient flows through the main biologicalgroups in the ecosystem. For Guam Atlantis two of four possiblemodules were parameterized [38]. The first is an ecological mod-ule that simulates primary ecological processes (consumption,production, waste production, migration, predation, recruitment,habitat dependency, and mortality). The reef-fish species wereaggregated in functional groups based on their diet, life historycharacteristics, and functional role [38]. The second is a physicaloceanographic module that represents the bathymetry, majorcurrents, salinity, and temperature and is based on the RegionalOcean Modeling System framework developed for the Coral Tri-angle [40]. The third module simulates fisheries (or other humanactivities) and was simplified as a fixed fishing mortality perfunctional group based on historical catches from shore-basedcreel surveys conducted by the Guam Division of Aquatic andWildlife Resources between 2010 and 2012 (DAWR). Due to a lackof data, this module did not include the effects of fishing gear onthe benthic habitat and species (e.g., physical damage to corals,ghost net fishing, and damage resulting from fish lines). Finally,the fourth Atlantis module simulates the socio-economic dy-namics, which typically represents commercial fisheries governedby economic rules, and was replaced by the fisher and diver be-havior models, outlined below.

The recently developed Atlantis model can correctly simulatekey dynamics in coral reef ecosystems around Guam [39]. Thesedynamics include ocean acidification [41], ocean warming [42],reef accretion and erosion [43], the relationship between thecomplexity of a reef ecosystem and its function to provide shelter

Table 1Breakdown of visitors by country [34] and the estimated number of people whowent diving [18].

Country Arrivals (FY2012) Dive participation (2002) (%) # Divers

Japan 901,683 5 45,084Korea 164,821 2 3296Hong Kong 8396 15 1259Taiwan 49,851 14 6979United States 50,967 8 4077

M. Weijerman et al. / Marine Policy 63 (2016) 8–1710

for fish species [44,45], the effects of nutrient and sediment inputon coral growth [46,47] and coral–algal dynamics (i.e., macroalgaecan overgrow corals, outcompete corals in nutrient-enriched wa-ters, prevent coral recruit settlement, and crustose-coralline algaeand, to a lesser extent, turf algae facilitate coral recruitment [48–50]).

Modeled output ecosystem metrics of Guam Atlantis werebased on a 30-year simulation run and averaged over the last fiveyears to account for interannual variation. Selected ecosystemmetrics indicative of reef status and resilience [51–53] include:species abundance (measured as total reef-fish biomass), numberof large fish (measured as the number of a slow growing species,represented by sharks, in the largest size class), and reef condition(measured as the ratio of calcifiers (corals and crustose-corallinealgae) to non-calcifiers (turf and fleshy macroalgae)). Those me-trics were augmented with two tourism-related metrics, abun-dance of charismatic species and reef-fish diversity (derived fromspecies richness, i.e., the number of functional groups present, andthe inverse of Pielou's Evenness: J‘¼H'/H’max where H' is theShannon–Wiener diversity index), to link to the diver behaviormodel. For the link to the fishery behavior model two socio-eco-nomic metrics were added: landings of targeted fish species andlandings of all species (including invertebrates; Fig. 2).

The qualitative human behavioral models leverage previouslypublished information and expert knowledge from people whohave worked with Guam's dive tourism sector or fishing sector (orboth). The disciplinary background of the experts included an-thropology, economics, resource science, sociology, and biologicalsciences. The two behavioral models focus on different aspects ofthe reef ecosystem; the tourism model focuses on reef condition

while the fishery model focuses on the extraction of reef-fishspecies. For the tourism model, the selected ecosystem metrics arekey to providing a high quality diving experience. For example, thepresence or absence of charismatic species [54], such as thehumphead wrasse, Cheilinus undulatus, and bumphead parrotfish,Bolbometopon muricatum; coral cover [55] (indicated by the eco-system metric reef condition), species abundance [56], and waterclarity [57] (implicitly included in reef condition, i.e., with highnutrients and/or sediments in the water column, clarity decreasesand algal growth is favored over coral growth reducing the reefcondition ratio).

For the fishery model, species abundance was selected, whichis expected to influence reef-fish fishery participation. The fish-eries relevant ecosystem metrics, landings of targeted fish speciesand total landings, were used to discuss consequences of changesin expected fisher behavior. A species was assumed to be a targetspecies when its representation in the landings of a particular geartype was greater than 20% (DAWR shore-based creel survey data).

Quantitative change was projected in the selected ecosystemmetrics to qualitatively explore six management scenarios (B–F)simulated using the Guam Atlantis model and compared to thestatus quo scenario (A) (Table 2).

As fisherman-specific catch data were not available, there wereno current estimates of daily or weekly catches to set a hypothe-tical bag limit for scenarios Bi, Bii, D and E. Instead, for eachfunctional group an annual allowable catch was set at 75% of thestatus quo landings at the end of a 30-year model run. This al-lowable catch was then divided by 52 to get a weekly bag limit.When this weekly limit was reached in the model run, fishing wasstopped for the remainder of the week. For size limits, fishing of all

EnforcementPiscivores

Corals Fleshy macroalgae

Sessile invertebrates

Detritus, bacteria

Zooplankton

Non-calcifiers

Planktivores

Phytoplankton

Management scenarios- Status quo (limited fishing MPs)- Size limit (1x input control, no MPs)- Bag limit (1x output control, no MPs)- Size and bag limit (2x controls, no MPs)- Watersheds restored &MPs- Watersheds restored & 2x controls- Watersheds restored & 2x controls & MPs- Watersheds restored & no fishing

Result variables calculated by the ecosystem model based on known landed spp

Variables calculated by Ecosystem model

Management scenarios evaluated by Ecosystem model

Total landings

Total landings targeted species

Calcifiers

Invertebrates

Benthic composition

Crustose-coralline algae Turf algae

Mobile invertebrates

Herbivores (incl. charismatic species)

CorallivoresInvertivores (incl.

charismatic species)

Species abundance

Reef condition

Charismatic species

Large fish (size distribution)

Reef-fish diversity

Fig. 2. Conceptual representation of the Guam Atlantis Coral Reef Ecosystem Model. Foodweb connections between (simplified) functional groups are shown by greenarrows. Black arrows indicate the linkages between the ecological model and the ecosystem metrics.

M. Weijerman et al. / Marine Policy 63 (2016) 8–17 11

fishes smaller than their size at maturity was stopped, includingthe seasonal runs on juvenile rabbitfish, goatfish and jacks.

For ease of interpretation and visualization, the 5-year meanvalues of the ecosystem metrics were normalized over all strate-gies resulting in values between zero (worst case) and one (bestcase).

4. Results

The results comprise two main components: (1) a descriptionof the theoretical dive tourism and reef fishing participation be-havior models; and (2) a description of the changes in the eco-system metrics as predicted by the Guam Atlantis ecosystemmodel for the different management scenarios. In the discussionthese results are brought together by examining the socio-ecolo-gical implications of the different management approaches.

4.1. Dive behavior model

A qualitative model linking the ecological, economic, and socialfactors that influence participation in dive trips in Guam is shownin Fig. 3. A full description of nodes in the model is provided inAppendix B and a description of the relationship between nodes inAppendix C.

Guam's dive sector is heavily dependent on healthy coral reefs,and there is a clear connection between environmental attributes(i.e., the ecological indicators in the ecosystem model) and diverwillingness to pay for diving on a reef [58]. Management can in-directly influence diver participation and the dive experience bychanging the’quality’ of the environment. For example, waterclarity (turbidity), several areas around Guam have turbidity issuesas a result of land-based pollution and changing water claritycould strongly influence the quality of the dive experience. How-ever, it is acknowledged that other marine management not fur-ther explored here, can also influence the quality of a dive

Table 2Details of simulated management scenarios. LBSP¼ land-based sources of pollution.

Scenario Presence of marinepreserves1

Existing levels of LBSP Fishing effort compared to statusquo (%)

Fishing of juvenile fish

A: Status Quo Yes Yes 100 Goatfish, rabbitfish, jacksBi: Bag and size limits No Yes 75 NoBii: Bag limit No Yes 75 Goatfish, rabbit fish, jacksBiii: Size limit No Yes 100 NoC: restored watersheds Yes No 100 Goatfish, rabbit fish, jacksD: Bag and size limits, restoredwatersheds

No No 75 No

E: Full regulations Yes No 75 NoF: No fishing, restored watersheds Yes No 0 No

1 Preserves are no-take areas except for seasonal take of juveniles and limited hook and line fishing from shore.

Fig. 3. Influence of different environmental and socioeconomic factors on participation in dive trips in Guam.

M. Weijerman et al. / Marine Policy 63 (2016) 8–1712

experience. These management approaches include, for instance,restricting diver behavior on the reef by placing limits on theirautonomy [59], controlling access to marine protected areas[60,61] or avoiding inter-sector conflict by spatially limiting con-tact with fishers or fishing gear [62].

Dive participation can be influenced by many other economicand social factors, some of which are outside the direct scope ofinfluence of resource managers, such as tourist visitation numbers.Tourist visitation numbers and country of origin are of particularinterest, as some tourists are more likely to go diving than others.

4.2. Reef fishing participation model

Similar to the diving model, a qualitative model describing thesocio-demographic, economic, and ecological factors influencingparticipation in Guam's reef fishery was developed (Fig. 4 andAppendices D and E).

Strategies for managing marine resource extraction and coralreef health can influence participation in reef fishing by affectingthe abundance of exploited and non-exploited species, and byaffecting where and when fishing can occur, what species (andsizes) can be taken, and the type of gear that can be used. Man-agement scenarios introducing bag and size limits restrict the

number and size of fish catch, which can influence how and wherefishers choose to fish [63,64]. Management of adjacent watershedscan decrease sedimentation and increase water quality, improvingnear-shore coral reef ecosystems that could lead to higher speciesabundance for reef fishing.

Spatial management of marine areas, such as marine preserves,can affect access to shoreline and nearshore fishing grounds [65].Access to fishing grounds is also affected by environmental vari-ables, including coastal features, such as cliffs [5], and adverseocean and weather conditions and by military exercises [66].

Ethnicity [5], gender, age [13] and whether one's family hasbeen traditionally engaged in fishing are socio-demographic vari-ables that play a role in determining participation in reef fishing.Economic variables that affect a fisher's decision to go reef fishinginclude the price of fish, which is partially determined by whetherit is high tourist season, opportunities for employment, and thecost of fuel [13].

4.3. Changes in ecological indicators as a result of management

Performance of scenarios that include restored watersheds out-competed the other scenarios in terms of better reef condition andspecies evenness (Fig. 5). The full regulation and no fishing and

Fig. 4. Influence of species abundance, economic and socio-demographic variables and participation in reef fishing on Guam.

0.0

0.2

0.4

0.6

0.8

1.0

speciesabundance

biomasscharismatic

species

landingstargeted fish

groups

total landings reef condition Evenness sp. richness size distr. shark

norm

aliz

ed e

ffect

size

A: Status Quo Bi: Bag & Size limit Bii: Bag limit Biii: Size limitC: Status Quo & WQ D: Bag & Size limit & WQ E: Full Regulations F: No Fishing & WQ

Fig. 5. Effect size based on normalized values of ecosystem metrics at the end of a 30-year simulation to allow comparisons of alternative management scenarios. Modeledscenarios are explained in “2 Methods” section.

M. Weijerman et al. / Marine Policy 63 (2016) 8–17 13

restored watershed scenarios had a positive effect on the speciesabundance, but performed worst of all scenarios with regard tototal landings (Fig. 5).

Compared to the status quo scenario (scenario A), removingmarine preserves while imposing bag and size limits (scenario Bi)resulted in a 12% increase in species abundance and in 2.5 timesthe biomass of charismatic species (Table 3). However, fish land-ings were 79% of the status quo landings and total landings (in-cluding invertebrates) dropped to 53% of the status quo landings.

5. Discussion

Effective management of tropical reef ecosystems under pres-sure from terrestrial and extractive marine activities is notstraightforward, especially with potentially competing reef-basedactivities. The shift towards ecosystem-based fisheries manage-ment (EBFM) demands quantitative tools to support policy andmanagement decisions. Ecosystem modeling and managementstrategy evaluation (MSE) are widely used in single species man-agement testing and are becoming increasingly used in support ofEBFM [67]. For EBFM evaluation, ecological models are coupledwith socio-economic models to uncover societal linkages [2,10].Evaluation of the potential effect of different management ap-proaches prior to implementation through modeling will reducethe chance of adverse or unexpected ecological or socio-economicoutcomes in the future and likely improve performance andcompliance [9].

While the focus of this work was on a case study in Guam, thenon-commercial reef-fish fishery and economic importance ofdiving also apply to many other tropical islands and coast linesmaking this approach generally applicable. EBFM that specificallyincludes the human dimension has gained traction among scien-tists, politicians and resource managers in the last decade [2,68].However, only a few models have attempted to couple biophysicaland socio-economic dynamics for coral reef ecosystems [69–71].Human dimension-centered models have examined different coralreef ecosystem states and the links to socio-economic conditionsand fishing participation [68], as well as the effects of gear typeson the overall reef condition [72]. Hence, the approach presentedin this study is novel as it includes the entire ecosystem fromplankton to humans and could be a valuable tool for EBFM.

Diminishing catches affecting the fishing sector have prompteda discussion on ways in which improved fishing and water qualityoutcomes may be achieved for Guam [28, J. Cameron, POC GuamCoral Reef Conservation Program, pers. comm. July 2014]. With theapproach outlined in this case study, key human behavior modelswere linked with a biogeophysical model to gain insight into theecosystem metrics that link the two systems and evaluation of theconsequences of management for socio-ecological effects in both

the fishing and diving sector. The impacts of the managementscenarios were quantified by means of ecosystem indices thatcould be meaningfully interpreted (although in a qualitativemanner) in the context of the main marine activities in Guam.

5.1. Trade-offs between marine sectors

At the heart of EBFM are the complex trade-offs between ob-jectives; these trade-offs can be between ecological and socio-economic objectives (as in this study), but competing uses can alsorequire trade-offs to be made between different socio-economicobjectives. It is clear that both Guam's dive industry and reeffishing activities are inherently reliant on healthy coral reef eco-systems. The number of ecological indicators that the dive sectoraims to maximize are more numerous (four in total) than thefishing sector, where species abundance (total reef fish biomass) isthe only direct link to participation in reef fishing. In evaluatingthese trade-offs, that should be taken into account.

For the tourism and recreation sectors, divers on Guam areimportant to Guam's economy and have demonstrated a will-ingness to make financial contributions towards marine manage-ment [58]. While the dive model presented here does not allow forbackwards interactions, it is important to note that given Guam'sreliance on tourism, the ecological attributes that indicate coralreef quality may influence other factors, such as, tourist visitationrates. Guam is a very popular diving location due to its high bio-diversity and a change in the perception of Guam as a lowerquality dive location could have a negative effect on the tourismindustry.

From the standpoint of the diving industry, a managementscenario where there is no fishing and no land-based source pol-lution provides optimal results with the highest values for ecolo-gical indicators. However, this scenario eliminates all reef-fishfishing which may be impractical and infeasible politically in ad-dition to not being economically optimal as commercial fishingalso contributes to the local economy, albeit a smaller amountthan tourism. Importantly, the absence of fishing would counterthe traditional use and identity of Guam's residents. Even thoughit is not easy to express the value of cultural fishing in monetaryterms, the maintenance of cultural activities has important links tocultural identity and a healthy community and society [37].

5.2. Interpreting alternative management scenarios

Alternative fisheries management scenarios will result in dif-ferent ecological outcomes. Input and output controls, such as sizeand bag limits, will limit reef fishing by restricting the size andnumber of fishes that can be taken [63,64]. Based on the ecosys-tem metrics for the management scenario, it is clear that imposinga simple input restriction (size limits) without any additional

Table 3Relative effect size of ecosystem metrics at the end of a 30-year simulation of the various management scenarios to the Status Quo scenario. Values are means of the last fiveyears of simulations. Overall effect size is the mean of the normalized ecosystem metric values as represented in Fig. 5.

Status quo Bag and sizelimits

Baglimit

Size limit Water-shedRest.

Bag and size and watershrest.

Full reg. No fishing and watershedrest.

A Bi Bii Biii C D E F

Total reef-fish biomass 1 1.12 1.13 0.94 0.99 1.12 1.31 1.33Biomass iconic species 1 2.50 2.97 0.34 1.14 3.09 3.18 7.56Landings targeted groups 1 0.79 0.80 1.05 1.08 0.80 0.79 0.0Total landings 1 0.53 0.67 0.71 0.98 0.52 0.02 0.0Reef condition 1 0.96 0.98 0.97 1.24 1.19 1.19 1.18Evenness 1 1.00 1.00 0.98 1.04 1.02 1.02 1.03Sp. richness 1 1.00 1.00 0.98 1.00 1.00 1.00 1.00Size distribution sharks 1 12.32 0.37 12.54 1.00 12.32 14.10 31.01Overall effect size 0.41 0.44 0.42 0.31 0.59 0.61 0.62 0.65

M. Weijerman et al. / Marine Policy 63 (2016) 8–1714

management measures will not improve the ecological outcomesfor the reef; in fact, it may prove to worsen outcomes compared tothe status quo, as fishing effort stays the same (so fishers will catchmore larger individuals to make up the forgone catches of smallerfishes). Combined input and output controls in the form of sizeand bag limits or bag limits on their own will only marginallyimprove the ecological outcomes for the reefs’ status compared tothe status quo. In practice, input management tools are relativelyeasy to implement [73] and could mean a fast change in reeffishing behavior, but the net result on overall participation infishing activities, compliance behavior, and location choice is un-certain. For example, under size limits, fishers may choose to avoidareas where they know there are higher numbers of small fish,which in turn may lead to localized depletion in areas with largerfish. Similarly, fishers may choose to fish closer to shore to reducefuel cost if there are bag limits – again causing localized effects.When areas are improving ecologically under the restored wa-tershed management, fishers may choose to direct their effort tothose areas. In other words, a transfer of effort as a consequence ofthe management scenarios is possible, which makes it difficult todetermine with certainty the total effect of controls on fishingparticipation.

The ecological metrics indicate that watershed restoration is animportant contributor to a healthy marine ecosystem. However,watershed restoration on its own is not adequate to address theproblems facing Guam's reefs and, in addition, may not achieveenough to provide the coral reef quality desired by the dive in-dustry. While coral reef quality increases under the status quo andimproved watershed scenario, total fish species biomass and thebiomass of charismatic species remain low. Given the importanceof these indicators for divers, selecting an alternative managementscenario that allows for some reduction in fishery landings to betraded off against an increase in the ecological attributes that arefavored by divers may be preferable to managers looking to bal-ance the needs of both sectors.

Surprisingly, the scenarios with full regulations including sizeand bag limits and watershed restoration with retention of exist-ing MPs (scenario E) and without the MPs (Scenario D) achievesimilar ecological outcomes. The main difference is in the total reeffish biomass that is 17% higher when existing MPs are retained,most likely because fish can grow larger in MPs [26]. RemovingMPs would increase shoreline and nearshore access to areas cur-rently closed to fishers. It is likely that fishers will begin fishing insome of the areas that were common fishing grounds prior tobeing closed to fishing when MPs were established [65]. Fishersmay also choose to fish with different gear and target different reeffish with the opening of MPs. The net result of reef-fishing parti-cipation in scenarios where MPs are opened cannot be de-termined. However, the potential for interactions between diversand fishers if MPs were opened may be concerning, as divers inother locations have expressed a preference to avoid such inter-actions [62].

Results show that there is little point in trying to manage thereef ecosystem and those who use it without also managing thewatershed. Over a 30-year timeframe, the three management ap-proaches with the most positive ecological impact all include re-stored watersheds. Three out of four ecosystem metrics importantto the dive sector will improve if size and bag limits are imposed,the watershed is managed, and existing marine preserves aremaintained. In the short term there will be some negative impactsparticularly on the fishing sector as a consequence of size and baglimits, but the long-term benefits for fishers and divers obtainedfrom greater species abundance are likely to outweigh these shortterm costs. Adopting watershed measures in addition to input andoutput controls distributes the burden for improving the reefstatus across multiple entities responsible for reef pressures.

6. Next steps

Despite the difficulties in predicting the overall behavioralchanges of fishers and divers under the different scenarios, theconceptual behavioral models (combined with the ecosystemmodel) provide a starting point for discussions with stakeholders.Effective resource management of coral reef ecosystems is highlydependent on effective involvement of local communities [74]. Thequalitative model of human behavioral drivers for reef fishing doesnot currently include probability distributions to enable a quan-titative analysis. However, the behavioral models can be trans-formed into Bayesian Networks (BN), which would enable quan-titative analyses of management approaches and the effects on theprobability of participation in the dive and fishing sectors in Guam[17,75]. Even though the probability density function for a numberof the variables was known, the conditional probabilities and re-lationships between mostly the social and cultural variables needsto be confirmed and tested by the local Guam community. Settingand testing the underlying probability distribution assumptions isan important component of developing a BN especially to promotelocal community ownership of the BN and modeling results.

7. Conclusion

Linking an ecological ecosystem model with socially and eco-nomically important human behavior gives us a better under-standing of changes in ecological performance due to managementof human-use activities. An integrated ecosystem model forGuam's fringing reef ecosystem enabled us to simulate alternativemanagement scenarios and assess the performance criteria onboth dive participation and participation in reef-fisheries. Whenthe objectives for reef ecosystems encompass conservation andextraction goals, an integrated ecosystem model can make thetrade-offs between different uses explicit. This allows managers toweigh the various performance measures and objectively considerthe trade-offs between resource users and determine a ‘bestmanagement solution’. From this study it is clear that the optimalmanagement solution for the reef ecosystem in Guam (and thedive tourism and fishing sector) is to combine input and outputcontrols, but most importantly, to restore the watershed and tothus reduce land-based ecological impacts.

Acknowledgments

Funding was provided to MW and SG by the NOAA Coral ReefConservation Program, project no. 817. We like to thank AdelHeenan and Rusty Brainard for their improvements to the manu-script. The scientific results and conclusions, as well as any viewsor opinions expressed herein, are those of the authors and do notnecessarily reflect those of NOAA or the Department of Commerce.

Appendix A. Supplementary material

Supplementary data associated with this article can be found inthe online version at http://dx.doi.org/10.1016/j.marpol.2015.09.028.

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M. Weijerman et al. / Marine Policy 63 (2016) 8–17 17

APPENDICES

Appendix A. List of participating organizations in the workshop and meetings conducted in

Guam in 2011 and 2014

Organization

NOAA Fisheries Pacific Islands Regional Office (PIRO)

NOAA Pacific Islands Fisheries Science Center (PIFSC)

NOAA Coral Reef Conservation Program (CRCP)

NOAA-PIFSC – Coral Reef Ecosystem Division

JIMAR - University of Hawai’i

POC Coral Reef Conservation, Western Pacific Fishery Management Council, Director of Dept.

of Chamorro Affairs

Guam Coastal Management Program (GCMP)

Guam Department of Agriculture

University of Guam Marine Laboratory

Humatak Community Foundation

Guam Preservation Trust

Naval Facility Andersen Air Force Base (AAFB)

USDA Natural Resource Conservation Service

War in the Pacific National Park (NPS)

Guam Environmental Protection Agency

Appendix B. Description of nodes in dive tourism behavior map. Starred (*) nodes connect

directly to the ecological model.

Node Description of node

Wreck diving The presence or absence of a wreck at a dive site. Guam has several

historic wrecks in Apra Harbor which are popular dive locations

Quality of the dive

experience

The combination of ecological and situational variables that influence

overall satisfaction

Previous dive

experience The total number of dives an individual has previously completed

Cost of dive

charter The price paid to participate in a dive

Tourist visitation

numbers The number of tourists visiting the island

Tourist country of

origin Tourists from different countries do not all have the same preferences

Age group The age of an individual (in years)

Price of

accommodation Price paid for hotel accommodations can vary throughout the year

Charismatic

species*

The presence or absence of charismatic species, such as, bumpead

parrotfish, Napoleon wrasse, sharks, turtles

Coral cover* The average of coral cover in the entire model domain

Species

abundance*

Species abundance is the standing stock biomass of the main species that

comprise the fishery target groups such as jacks, parrotfish, groupers,

surgeonfish, goatfish, invertebrates (e.g. lobster) and non-target

groups. The standing stock biomass changes over time due to habitat

degradation and extraction.

Clarity of the

water

Sediments and algal blooms can reduce the clarity of the water, and thus

visibility.

Tourist season Peak season is January to May; Off season is July to November; June and

December are shoulder months.

Flight availability The number of flights arriving in Guam per month

Access to diving

locations

Access to coastline areas and potential dive sites is restricted by the natural

features of the coastline in Guam, ocean and weather conditions, and

military/security access controls.

Watershed

condition

A description of the watershed as degraded or not. Degraded watersheds

are assumed to have the same run off of sediments and nutrients as present

conditions. When watersheds are restored, we assume no additional

sediment and nutrient inputs.

Marine preserves

Guam has 5 marine preserves: Tumon Bay MP, Piti Bomb Holes MP, Pati

Point MP, Sasa Bay MP, and Achang MP. There are specific rules

regulating fishing and other activities for each one. They cover

approximately 16.3% of Guam's coral reef habitat from 0 to 30-m depth.

Ocean and weather

conditions

Ocean and weather conditions that may change on a daily or seasonal

basis, such as wind speed and direction, wave height, tides, and visibility;

Waters in some areas around the island are too rough for diving during

much of the year.

Coastal features Access to coastline areas and potential dive sites is restricted by the natural

features of the coastline in Guam.

Access areas

closed by military

Areas of the shoreline, territorial waters (out to 3 nm), and federal waters

(3 - 200 nm) that are closed to fishing activities by the U.S. military and/or

territorial and federal security agencies (e.g., the U.S. Department of

Homeland Security).

Enforcement of

marine preserves

The effectiveness of enforcement of rules regulating fishing and boating

activities.

Appendix C. Description of connection between nodes of dive tourism behavior map

Variable A Variable B Connection between variables Reference

Enforcement Marine

preserves

The effectiveness of enforcement can determined if dive

charters respect and observe the rules regulating fishing

and other activities within the marine preserves.

Expert opinion

Marine

preserves

Species

abundance

The establishment (and enforcement) of marine preserves

may influence the overall abundance of species and in

particular in species that complete their life cycle within

the marine preserve boundaries. Moreover, spillover

effects may lead to a greater biomass or fish abundance of

species just outside of the marine preserve boundaries.

Tupper 2007

Marine

preserves

Charismatic

species

The establishment (and enforcement) of marine preserves

influences the overall abundance of charismatic species

and in particular in species that complete their life cycle

within the marine preserve boundaries.

Tupper 2007

Marine

preserves Coral cover

There is little evidence that marine preserves increase

coral cover, as coral cover increase is related to herbivore

biomass. However, herbivore biomass increases within

marine preserves.

Gilmour et al. 2013

Watershed

conditions Turbidity

Different types of land use will have a different effect on

runoff and thus ocean turbidity. Turbidity created by

different land uses can be a problem in some areas of

Guam. If the watershed is in good condition this will

decrease runoff and thus turbidity.

Burdick et al. 2008

Oceans and

weather

conditions

Turbidity Windy and stormy conditions can increase ocean

turbidity. Wolanski et al. 2003

Oceans and

weather

conditions

Access to

diving

locations

Changes in ocean and weather conditions occur on a daily

basis. Some weather conditions will not allow dive

activities to take place. In addition, near shore waters on

the east side of the island are too rough for diving.

Expert opinion

Coastline

features

Access to

diving

locations

Cliff lines make up a significant portion of the coastline

and prevent coastal access for dive charters, particularly

on the east side. The most popular dive destinations are

on the west side of the island due to the presence of

fringing reefs and bays and are accessible for dive charter

for most of the year.

http://www.mdaguam.com/content/guam-

beach-dives

Areas closed

by military

Access to

diving

locations

Military areas are off limits and no access can be gained

for dive charters. Further, construction in preparation for

the military buildup has also inhibited access to municipal

boat ramps, limiting the number of boat access points.

Expert opinion

Access to

diving

locations

Cost of dive

charter

Decreased access to dive grounds from the shoreline can

increase the distance boats need to travel, in turn,

increases fuel use. With higher fuel prices are likely to be

passed on to the customers.

Expert opinion

Tourist

season

Cost of dive

charter

In peak tourist season the cost of dive charters is higher as

demand for charters is relatively higher. Expert opinion

Tourist

season

Price of

accommodat

ion

In the peak tourist season the price of accommodation is

higher. Expert opinion

Tourist

season

Flight

availability

In peak seasons there are more flights available to bring

tourists to Guam. Expert opinion

Price of

accommodati

on

Tourist

visitation

numbers

If prices of accommodation are comparatively high this

means that tourism visitation is likely to be negatively

affected.

Expert opinion

Flight Tourist If more flights are available this is likely to increase the Expert opinion

availability visitation

numbers

number of tourist visiting Guam.

Flight

availability

Tourist

country of

origin

There are more flights to Guam from some countries thus

influencing the country of origin of the tourists. Expert opinion

Wreck diving Participation

in dive trips

There are a number of popular wreck dives with historical

significance in Apra Harbor, so the presence/absence of a

wreck could also influence participation in dive trips.

http://www.nps.gov/submerged/Parks/WAP

A.html

Tourist

visitation

numbers

Participation

in dive trips

With higher tourist number the demand for dive trips is

also likely to increase. Expert opinion

Cost of dive

charter

Participation

in dive trips

More expensive dive trip costs is likely to negatively

affect participation in dive trips. Rudd and Tupper 2002

Previous dive

experience

Participation

in dive trips

People with previous dive experience are more likely to

participate in new dive experiences and partake in dive

trips on their holidays.

Expert opinion

Age

Previous

dive

experience

Age group influences previous dive experience with older

divers generally having completed more dives. S. Grafeld unpublished data

Quality of

the dive

experience

Participation

in dive trips

Positive dive experiences will mean that it is more likely

that the tourist will participate in a dive trip. Expert opinion

Size of dive

group

Quality of

the dive

experience

Previous studies have included the size of the group on a

dive charter as a measure of the quality of the dive

experience (with a higher WTP for smaller groups).

Rudd and Tupper 2002, Schuhmann et al.

2013

Charismatic

species

Quality of

the dive

experience

Charismatic species are important contributors to a dive

experience. Some divers will value the sighting of

charismatic species most as part of the dive trip.

$5.40 more/dive to see more Napoleon

wrasse

S. Grafeld unpublished data

Coral cover

Quality of

the dive

experience

The condition and extent of coral cover will increase the

aesthetic quality of the reef and thus increase the quality

of the dive experience.

Parsons and Thur 2008

Species

abundance

Quality of

the dive

experience

The more species are visible and present on a dive – the

more divers are likely to enjoy the experience.

$6.45 more/dive for a change from low to

high fish biomass

$6.23 more/dive for a change from low to

high fish species diversity

S. Grafeld unpublished data

Turbidity

Quality of

the dive

experience

If turbidity is high- visibility is low and likely to decrease

the quality of the dive experience.

$10 on average (+/- $5) towards sediment

reduction projects

S. Grafeld unpublished data

Tourist

country of

origin

Tourist

visitation

numbers

There are more tourists from some countries than others

(i.e. Japanese tourists make up the largest group).

https://www.fhb.com/en/assets/File/Marketi

ng/FHB_2013-14_GuamEconForecast.pdf

Appendix D. Description of nodes in the fishery behavior map. Starred (*) node connects to

ecological model.

Node Description of node

Enforcement The effectiveness of enforcement of rules regulating fishing and boating

activities.

Areas closed by

military/security

Areas of the shoreline, territorial waters (out to 3 nm), and federal waters

(3 - 200 nm) that are closed to fishing activities by the U.S. military

and/or territorial and federal security agencies (e.g., the U.S. Department

of Homeland Security).

Ocean and weather

conditions

Ocean and weather conditions that may change on a daily or seasonal

basis, such as wind speed and direction, wave height, tides, and visibility;

waters in some areas around the island are too rough for fishing from

small boats during much of the year.

Coastline features Access to coastline areas and nearshore fishing areas is restricted by the

natural features of the coastline of Guam.

Access to shoreline

and fishing grounds

Whether or not fishers can enter and/or utilize coastal and marine areas

for fishing activities. Types of areas include coastal access roads,

beaches, boat ramps, docks/piers, and marine areas.

Tourist season Peak season is January to May; Off season is July to November; June and

December are shoulder months.

Price of fish The price for which fish are bought and sold on Guam. This depends on

several factors, including seasonal availability of fish, time of year/tourist

season, and outlet to which fish is being sold (Guam Fishermen's Co-op

versus restaurants versus other markets).

Fuel cost The cost of fuel used to run marine vessels. This is the main operating

cost incurred in boat-based fishing on Guam.

Employment

opportunities

1) Whether or not fishers earn income from non-fishing employment, 2)

Whether or not that employment provides them with money beyond what

is needed to meet regular expenses, allowing them to have "free time"

and extra income.

Age Age of fisher (in years)

Gender Gender of fisher

Fishing tradition Whether or not one comes from a "fishing family"; whether one's family

members (especially older family members) are fishers.

Node Description of node

Ethnicity Ethnicity of fishers; people of some ethnicities are more likely to be

engaged in fishing in Guam.

Species abundance Species abundance is the standing stock biomass of the main species that

comprise the fishery target groups such as jacks, parrotfish, groupers,

surgeonfish, goatfish, invertebrates (e.g. lobster) and others. The

standing stock biomass changes over time due to habitat degradation and

extraction.

Participation in reef

fishing

Any activity that involves the collection of reef species. On Guam, this

includes commercial fishing and non-commercial fishing. Fishers often

use multiple fishing gears and target multiple marine species during a

single fishing trip. Fish may be used for subsistence, given away, or sold

depending on a variety of trip-based factors. When and where one fishes,

which methods are used, and which species are targeted depends on

several factors, including the experience level of fishers and access to

resources required to fish (e.g., boat, gear, fuel).

Appendix E. Description of connections between nodes in the fishery behavior map. Starred (*) node connects to ecological

model.

Variable A Variable B Connection between variables Reference

Enforcement Management

scenarios

The effectiveness of enforcement can determine if fishers respect

and observe the rules regulating fishing activities.

Charles et al. 1999, Sutinen

and Kuperan 1999, Hatcher

et al. 2000

Management

scenarios

Species

abundance

Different management scenarios will affect species abundance in

different ways. For example, the existence (and enforcement) of

marine preserves may influence the overall abundance of species,

particularly for species that complete their life cycle within the

marine preserve boundaries. Or, size-based controls on species

influence the overall abundance of those species by limiting the

fish allowed to be landed to those of a specific size. With a build-

up of larger (older) individuals larval quality and survivorship

increases. Leaving the small, immature fish will increase the

spawning biomass.

Berkeley et al. 2004,

Birkeland and Dayton 2005,

Taylor et al. 2012, Williams

et al. 2012

Management

scenarios

Access to

shoreline and

fishing

grounds

Some management scenarios (such as the existence/expansion of

MPs) may prevent fishers from accessing certain shoreline and

nearshore areas, sometimes restricting access to common or

traditional fishing grounds.

Expert opinion and personal

observation

Areas closed

by

military/securi

ty

Access to

shoreline and

fishing

grounds

These kinds of closed areas limit the ability of fishers to access

and fish within fishing grounds. Further, construction in

preparation for the military buildup has also inhibited access to

municipal boat ramps, restricting boat access to nearshore fishing

grounds and fewer access points. Fishers have to make longer

boat trips to get to their fishing locations.

Expert opinion and personal

observation

Ocean and Access to Changes in ocean and weather conditions occur on a daily and Expert opinion

Variable A Variable B Connection between variables Reference

weather

conditions

shoreline and

fishing

grounds

seasonal basis and contribute to fishers' decisions regarding

whether to go fishing and where they will fish. Some nearshore

waters on the east side of the island are too rough for fishing from

small boats for approximately 9 months of the year, on average.

Coastline

features

Access to

shoreline and

fishing

grounds

Coastline features determine the extent of coastal access for

fishers. For example, cliff lines make up a significant portion of

the coastline and prevent access to adjacent fishing grounds.

Allen and Bartram 2008

Access to

shoreline and

fishing

grounds

Fuel cost Decreased access to shoreline and fishing grounds can increase the

distance boats need to travel to preferred fishing grounds; this, in

turn, increases fuel use. With higher fuel prices, the cost to travel

further distances increases. Fuel is the main operating cost

incurred in fishing on Guam. Increased fuel costs influence where

and how often fishermen decide to fish.

Hospital and Beavers 2012

Expert opinion

Access to

shoreline and

fishing

grounds

Participation

in reef

fishing

Access to fishing grounds can affect fishers’ decision to fish via

expectations for: financial profit, catching fish as food, and/or

passing on fishing tradition. Additionally, access affects decisions

regarding when and where to fish, which gear to use, and which

species to target. Further, restrictions to access may focus fishing

in smaller areas, encouraging competition and local depletion in

remaining open areas.

Halpern et al. 2004, Allen

and Bartram 2008

Tourist season Price of fish Tourist season affects the price of fish because prices tend to be

higher during high season when the demand is high for certain

species.

Expert opinion

Variable A Variable B Connection between variables Reference

Price of fish Participation

in reef

fishing

The current price of fish may determine: 1) whether one decides to

go fishing or not, 2) the fishing method used (including location,

gear used, and species targeted), and 3) what is done with the

catch once landed (kept for household consumption, given

away/shared, sold).

Expert opinion

Employment

opportunities

Participation

in reef

fishing

Fishing activities can be affected by: 1) whether or not fishers earn

income from non-fishing employment, and 2) whether or not that

employment provides them with money above and beyond what is

needed to meet regular expenses. Fishers who hold jobs that

provide them with extra income, and who have "free time," are

able to buy and maintain a fishing boat and fishing gear, and

afford the expenses of fishing trips. The fish they catch may be

used for household consumption, given away, or sold for extra

income to recoup fishing trip costs. On the other hand, fishers

who do not earn sufficient income from non-fishing employment

may have a greater incentive to fish to provide food for their

households.

Expert opinion

Fuel cost Participation

in reef

fishing

Fuel is the main operating cost incurred in boat fishing on

Guam. As fuel prices increase, less of the fuel cost is recovered

either when selling fish or when used as food. Above some price

for fuel, fishers may decide not to go out fishing because it is not

worth the investment in fuel. Therefore, increased fuel costs

influence where and how often fishers decide to fish, which gear

to use, and which species to target.

Hospital and Beavers 2012

Age Participation

in reef

fishing

In general, younger people are more likely to fish than older

people, especially physically-demanding activities such as spear

fishing.

Expert opinion

Variable A Variable B Connection between variables Reference

Gender Participation

in reef

fishing

Men are much more likely to fish than women. Expert opinion and personal

observation

Fishing

tradition

Participation

in reef

fishing

Individuals are more likely to fish if they come from a "fishing

family," and/or if other members of their families are fishers.

Expert opinion

Ethnicity Participation

in reef

fishing

Individuals are more likely to fish if their ethnicity has been

historically engaged in fishing.

Allen and Bartram 2008

Species

abundance*

Participation

in reef

fishing

The overall abundance of marine species may determine: 1)

whether one decides to go fishing or not, 2) the fishing method

used (including location, gear used, and species targeted), and 3)

what is done with the catch once landed (kept for household

consumption, given away/shared, sold).

Expert opinion

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Allen, S. and P. Bartram. 2008. Guam as a fishing community. Pacific Islands Fish.Sci. Cent. , Pacific

Islands Fis. Sci. Cent., NMFS, NOAA, Honolulu HI 96822-2396.

Berkeley, S. A., M. A. Hixon, R. J. Larson, and M. S. Love. 2004. Fisheries sustainability via protection

of age structure and spatial distribution of fish populations. FISHERIES 29:23-32.

Birkeland, C. and P. K. Dayton. 2005. The importance in fishery management of leaving the big ones.

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Lundblad, J. McIlwain, J. Miller, D. Minton, M. Nadon, N. Pioppi, L. Raymundo, B. Richards, R.

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